oops in codeigniter

could you share oops in codeigniter?

Object Orientated programming or mistakes?

Read some example class in the core CI and find them. OR why dont you build some libraries class ? it is everywhere.
Here let's do it:

Code:

/*
**Foo.php
*/
class Foo{
function tellFoo(){
   return 'Im a foo';
}
}
//Ok put it in library folder
then you can call it in any controllers or models so on such as

class Hello extends CI_Controller{
function __construct(){
    $this->load->library('foo');
}
function greet(){
    print $this->foo->tellFoo();//use it with func tellFoo()
}
}